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    <title>Document</title>
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    <script>
        let arr = ['a','b',3,4,5,6,7,8];

        console.log(arr.keys());
        console.log(arr.keys().next()); //数组下标

        console.log(arr.values().next());//数组值

        let obj = arr.entries();
        console.log(obj.next()); //[0, 'a'] 数组的索引和值 组合数组
        console.log(obj.next()); //[1, 'b']
    </script>
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